The AUXPROC option, followed by a fullword address of an auxiliary
processing routine, allows that routine to receive control from DMSSEE before any device I/O is performed. At the of its processing.
the auxiliary routine returns control to DMSSEB signaling whether or not I/O bas been performed. If it has not been done, DMSSEB performs the
appropriate device I/O. When control is received from DMSSEB, the general-purpose registers
contain the following information: GPR2 Data Control Block (DCB) address GPR3 = Base register for DMSSEB GPR8 = CMS OPSECT address GPR11 File Control Block (FCB) address GPR14 Return address in DMSSEB GPR15 Auxiliary processing routine address
all other registers = Work registers
The auxiliary processing routine must provide a save area in which to
save the general registers; this routine must also perform the save
operation. DMSSEB does not provide the address of a save area in
general register 13, as is usually the case. When control returns to DMSSEB, the general registers must be restored to their original values.
Control is returned to DMSSEB by branching to the address contained in
general register 14. GPR15 is used by the auxiliary processing routine to inform to DMSSEE of the action that has been or should be taken with the data block as
follows: Action GPR15=O No I/O performed by AUXPROC routine; DMSSEB will perform I/O. GPR1S(O GPR15>O I/O performed by AUXPROC routine and error was encountered. DMSSEB will take error action. I/O performed by AUXPROC routine with residual count in GPR15; DMSSEB returns normally. GPR15=64K I/O performed by AUXPROC routine with zero residual count. Part 3. Conversational Monitor system (CMS) 283

DOS /VS Support under eMS eMS supports interactive program development for DOS/VS Release 31, 32. 33 and 34. Tbis includes creating, compiling, testing. debugging. and
executing commercial application programs. The DOS/VS programs can be executed in a eMS virtual machine or in a CMS Batch Facility virtual
machine. DOS/VS files and libraries can be read under eMS. VSAM data sets can
be read and written under CMS. The eMS DOS environment (called CMS/DOS) provides many of the same
facilities that are available in DOS/VS. However, CMS/DOS supports only
those facilities that are supported by a single (background) partition.
The DOS/VS facilities supported by CMS/DOS are: • DOS/VS linkage editor • Fetch support • DOS/VS Supervisor and I/O macros • DOS/VS Supervisor control block support • Transient area support • DOS/VS VSAM macros
This environ.ent is entered each time the eMS SET Des ON command is
issued; VSAM functions are available in CMS/DOS only if the SET DOS ON (VSAM) command is issued. In the CMS/DOS environment, CMS supports many DOS/VS facilities, but does not support OS simulation. When you nO longer need DOS/VS support under CMS, you issue the SET DOS OFF co •• and
and DOS/VS facilities are no longer available. CMS/DOS can execute programs that use the sequential (SAM) and virtual storage access method (V SAM) , and can
libraries.
access lIethod access DOS/VS CMS/DOS cannot execute programs that have execution-time
restrictions, such as programs that use sort exits, teleprocessing
access methods, or multitasking. DOS/VS COBOL, DOS PL/I, and Asse.bler
language programs are executable under CMS/DOS. All of the CP and CMS online debugging and testing facilities (such
as the CP ADSTOP and STORE commands and the CMS DEBUG environment) are
supported in the CMS/DOS environment. Also, CP disk error recording and
recovery is supported in eMS/DOS. With its support of a CMS/DOS environment, ces becomes an important
tool for DOS/VS application program development. Because CeS/DOS was
designed as a DOS/VS program development tool, it assumes that a DOS/VS system exists, and uses it. The following sections describe what is supported, and what is not.
284 IBM VM/370 System Guide